I am planning on buying the Asus VG278H or the Samsung SyncMaster S27A950D, still haven't decided yet. Asus gives better 3D and integrated nVidia support, but Samsung gives better 2D.. but that is not my question.

What I really need to know is how big the performance hit for 3D on my pc is. I am a big fan of at least 50 fps (60 or more pref.), but since my computer is getting old I am afraid it will have to big of a negative impact on my fps.
Do I need to wait with buying a 3D monitor till I get some better gear (though my pc is doing just great now with all new games) or do I need to wait on better monitors or newer techniques?

Specs of my pc (also to the left I believe, but can't check that while making this post :p):

That's about it I guess. This setup usually gives me 50+ fps in most games with which I am satisfied. But I utterly hate playing on lower then 50fps and if 3D would do that then I am not buying a monitor at all.

Thanks in advance for taking the time to read this!

Edit:One sidenote, I don't care for those silly ultragraphic options in most new games, they usually give just a tiny bit of extra eyecandy but cost an exponential amount of processing power. Know that I turn those off anyway. So I have some extra processing power for 3D that way.

I'm a bit surprised no-one replied to this.
Just did a simple stat fps command with an old game (Deus Ex) and the performance went from 120FPS in 2D to 60FPS in 3D. It's not that surprising really, it has to render twice the content of 2D.

Well i'm having gtx 580 q6600@3.2, and all games are running at 1080p full/ultra at 60FPS in stereoscopic 3d so no problems about the performance hiit,only games that could experience slowdowns is witcher 2 ,skyrim with graphical mods..batman battlefield crysis metro trine shogun 2 all work flawlessly so no problems should be on your side with gtx 480

and the reason why you get 60fps is becase when you turn on vsync it automaticly locks the refresh rate at 60fps if you have 120hz monitor,best thing that happened to me is the latest beta driver for nvidia 301.32 they eleminated 80% of ghosting and improved performance with Adaptive Vsync

Yeah right... How can you say that? I have a 560 Ti and a lot of games are running between 60 and 80 FPS on average. That's between 30 and 40 FPS in 3D if I keep the same settings. How do you think a 480 would perform?
Just divide the FPS you're getting in 2D in half and you know how 3D will perform.